How to seal a beta type engine? Need help!

[kennethkye]

Hi everyone,

I'm currently doing a project where I need to fabricate a beta type stirling engine with the power piston diameter of 20mm and length of 12mm. The power piston has a 4mm hole at the center that allows the displacer rod(4mm) to pass through it.

Do anyone of you know the methods to seal the power piston and also the displacer rod that passing through it? Thanks in advance!

[somi]

I'm not sure of the construction of the displacer, but it looks as though it is a metal tube, the main thing is that it must not rub on the inside of the cylinder. The rod must move freely through the gland, but have minimal leaks of air.

[TheGermanDude]

Hi,

try using a fine whire for the displacer connecting rod. so the hole in the working piston can be smaler.

The working piston must fit perfect in the working cylinder and have low friction. It must be created with high precision.

greetings

[Ian S C]

kennethkye, Ideally you would drill the gland say 3.5 mm, then bore it in the lathe with a little boring bar. Maybe more likely I would perhaps drill it to 4 mm, taking it in stages, drill 3 mm first. Then you will find that a 4 mm rod will not go through a 4 mm hole, If you look in my gallery you will see a tool makers reamer, and if you made the gland from brass, you can make a reamer like this from the same steel as the displacer rod. As you file the sloped bit on the end of the reamer, it will leave a little bur, leave that, as long as it is very small, pass the reamer through the hole, then try the rod, if it is too tight pass the file over the slope again and re-ream the hole.
I'v used a number of materials for these glands: PTFE/ Teflon. Brass, cast iron, and bronze.
Ian S C

[reeta]

im also going to use your ratios and totally rebuild the smaller engine after a trip to my favourite scrap metal merchants this coming weekend for some more brass